| 摘要 |
PURPOSE: To produce a metallic magnetic powder excellent in magnetic characteristics by forming a metallic compd. layer contg. Co on the surface of a needle or spindle hydrous iron oxide grain, then heating and reducing the coated grain under specified conditions. CONSTITUTION: An acidic soln. of such water-soluble compds. as sulfate and nitrate contg. a Co compd. is added to an alkaline slurry of needle or spindle hydrous iron oxide to form a Co compd. layer on the surface of the hydrous iron oxide grain, and an aq. soln. of a dispersed metal precursor is formed. The soln. is then regulated to pH11 to 13 with NaOH, etc., oxidized at 80 deg.C while blowing air, etc., dispersed, filtered and dried to obtain the metal precursor, the grain size of the precursor is controlled to 48-64 mesh, for example, and the grain is heated to 500 deg.C in the air and then reduced in an H2 , gas current. The grain is finally heated in an N2 gas current contg. a trace amt. of O2 to oxidize its surface, and the metallic magnetic powder for a magnetic recording medium excellent in coercive force and dispersibility is produced. |
